good lord...
why did America threaten to invaded Cuba? A: because Russia put nuclear weapons in Cuba pointed at America.
Why did Russia threatento invaded Ukraine? (Fixed it for you)
A: because Putin wanted to gain valuable land and did not want a Western democracy on his doorstep.
See the difference?
The hole I see in this consideration is that Russia expressed no territorial ambitions on Ukraine prior to the coup in 2014.
From 2014-2021 they continued pushing for a political settlement that would see Luhansk and Donetsk
remaining as part Ukraine, with the stipulation that Ukraine remain a neutral nation.
The Russian foreign policy goal since 1945 has been to maintain a buffer between themselves and the West (the source of roughly 3 Holocausts worth of Russian deaths in WW2).
That was why Baker made the assurances in 1990 about not expanding NATO in exchange for Soviet withdrawal from East Germany.
Just as the US saw Soviet bases in Cuba, on our doorstep, as intolerable and worthy of going to war to stop, the Russians have long declared the same about Ukraine, for the exact same reasons. It's why our current CIA Director (formerly Russian ambassador) lobbied against it within multiple US administrations.
It's precisely because they've made their concerns so public for so long, that's hard for me to conclude anything but that the neocons provoked this war deliberately, against the advice of people whom history has proven to be correct, with the expectation they could manage it from spiraling out of control.
Given their miscalculations over the last 20 years, we're at greater risk of nuclear war than anytime since the U.S. took military steps to prevent the establishment of Soviet military bases in Cuba.